Function postorder

compat/regex/regcomp.c:1222–1252

Our parse trees are very unbalanced, so we cannot use a stack to implement parse tree visits. Instead, we use parent pointers and some hairy code in these two functions. */

      ret = calc_inveclosure (dfa);
    }

  return ret;
}

/* Our parse trees are very unbalanced, so we cannot use a stack to
   implement parse tree visits.  Instead, we use parent pointers and
   some hairy code in these two functions.  */
static reg_errcode_t
postorder (bin_tree_t *root, reg_errcode_t (fn (void *, bin_tree_t *)),
	   void *extra)
{
  bin_tree_t *node, *prev;

  for (node = root; ; )
    {
      /* Descend down the tree, preferably to the left (or to the right
	 if that's the only child).  */
      while (node->left || node->right)
	if (node->left)
	  node = node->left;
	else
	  node = node->right;

      do
	{
	  reg_errcode_t err = fn (extra, node);
	  if (BE (err != REG_NOERROR, 0))
	    return err;
	  if (node->parent == NULL)
	    return REG_NOERROR;
	  prev = node;
	  node = node->parent;
	}
      /* Go up while we have a node that is reached from the right.  */